Mobile communication systems have been developed to provide voice services while ensuring the activity of a user. However, the mobile communication systems have been expanded to their regions up to data services as well as voice. Today, the shortage of resources is caused due to an explosive increase of traffic, and more advanced mobile communication systems are required due to user's need for higher speed services.
Requirements for a next-generation mobile communication system basically include the acceptance of explosive data traffic, a significant increase of a transfer rate per user, the acceptance of the number of significantly increased connection devices, very low end-to-end latency, and high energy efficiency. To this end, research is carried out on various technologies, such as dual connectivity, massive Multiple Input Multiple Output (MIMO), in-band full duplex, Non-Orthogonal Multiple Access (NOMA), the support of a super wideband, and device networking.
The radio link availability of the current LTE/LTE-A system entirely depends on network coverage provision probability, which reaches to 95%.
In addition, it is assumed that the radio reliability of the LTE/LTE-A system may provide sufficient reliability with H-ARQ retransmission in the case of Unicast data through a PDSCH, without distinction of a control plane (C-plane) and a user plane (U-plane), to which Block Error Rate (BER) of 10−3 is applied.
Currently, although the LTE/LTE-A system is greatly invigorated and has been providing various services, it is unable to provide a connectivity that guarantees the reliability for satisfying Mission Critical Services (MCSs) always for all time durations.
This is because the LTE/LTE-A system itself is designed to provide relatively good connectivity with respect to most of times, and accordingly, the LTE/LTE-A system provides data rate close to ‘0’ in a particular Poor Coverage in which severe interference is undergone or network resources are in overload state.
In the future, it is expected that new MCSs largely depending on availability/reliability of radio link are advent for satisfying a high level of communication quality, and an evolution of wireless technology is required, which may accommodate such new MCSs.